1. Field of the Invention
This invention relates generally to hammer mills and is particularly concerned with a symmetrical cap for protecting the ends of the spiders which make up the rotor assembly for the hammermill.
2. Description of the Prior Art
Hammermills of the type contemplated herein are used to break up large metal objects such as automobile bodies into small fragments. This is of particular importance in the disposal of old cars and the recovery of usable pieces of scrap metal. These shredders generally include a housing, a rotary hammer assembly mounted for rotary motion in the housing and a drive assembly for rotating the hammer assembly past grate bars which cooperate with the hammers to fragment or shred the metal objects.
The hammer assembly generally includes a number of spiders which are mounted in a spaced relation on a hammermill drive shaft. Each spider includes a number of arms which extend radially outwardly in a spaced relation to provide a support for the hammers. It has been generally known that the life of the spider arms is limited due to the continuous impact of the arms with the fragmentized metal. The life of the spider has been extended by the use of protective caps or tips to protect the arms from impact with the metal fragments as shown in my copending application Serial No. 07/266,119 as well as in U.S. Pat. No. 3,727,848 entitled "Hammermill with Replaceable Spider Arm Tips" issued Apr. 17, 1973; U.S. Pat. No. 4,290,545 entitled "Replaceable Protective Means for End Disc Shredder" issued Sept. 16, 1980; and U.S. Pat. No. 4,222,530 entitled "Method of Attaching a Protective Cap to a Shredder Component" issued Sept. 22, 1981. In all these devices, the cap is mounted on the spider arm and is replaced when worn.
U.S. Pat. No. 4,056,232 entitled "Protective Device for Rotary Hammer Breaker" issued on Nov. 1, 1977, describes a hammerbreaker including a plurality of discs driven upon a rotary shaft and a plurality of rods extending through the discs parallel to the rotor shaft and radially spaced therefrom. A plurality of hammers are pivotably mounted on the rods between the discs. The periphery of the discs are protected by a plurality of shields mounted on the rods between the discs and extending over a part of the periphery of each disc. The shields must be strengthened by webs to prevent breaking off at the ends of the shields.